1. Field of the Invention
The present invention relates to fluid transfer devices, and more particularly to a dual injection airlift pump having both radial and axially peripheral air or gas injection.
2. Description of the Related Art
The general concept of the airlift pump has been known for quite some time. Airlift pumps generally comprise a vertically oriented tubular pump body through which the liquid that is being pumped passes. One or more air (or other gas) injection passages are provided in or with the pump body. The airlift pump contains no moving parts, but rather depends upon the injection of air (or other gas) into the pump interior to lift a liquid passing through the pump. The lighter air or gas bubbles upwardly through the liquid in the tubular pump body, increasing the buoyancy of the liquid and causing it to rise in the vertically oriented tubular body. Pumps operating by this principle do not produce high pressure heads, but are capable of moving volumes of liquid reasonably efficiently with relatively low energy input.
Nevertheless, there is room for increased efficiency with conventional airlift pumps. The conventional airlift pump includes a single stage of air or gas injection, generally by means of an externally disposed air delivery line that extends downward along the outside of the pump body to inject air into the bottom or inlet end of the pump. The provision of only a single point discharge for the air or gas entering the pump body results in a relatively narrow bubble stream through the liquid in the pump body, with such a narrow stream failing to add buoyancy and entrain the majority of the volume of liquid in the pump body. Moreover, the expanding gas bubbles at the lower end or inlet of the pump body tend to produce at least some restriction to liquid flow entering the pump.
Thus, a dual injection airlift pump solving the aforementioned problems is desired.